Phase shift mask blank, photo mask blank, and manufacturing apparatus and method of blanks

ABSTRACT

There is provided a manufacturing apparatus and method able to manufacture a phase shift mask blank in which a total number of particles and pinholes having a diameter larger than about a half of an exposure wavelength in a light semi-transmission film is 0.1 or less per square centimeter. In a DC magnetron sputtering apparatus for manufacturing a halftone phase shift mask blank, for example, a target plane is disposed downwards with respect to a gravity direction, a whole-surface erosion cathode is used, a corner portion  5   a  of an end of a target and a corner portion of an earth shield are chamfered (R processed), a target end  5   b,  an exposed backing plate surface  4   b  and the surface of an earth shield  12  are roughened, and the earth shield  12  is disposed above a target plane d (on a backing plate side).

[0001] This application claims the Paris convention priority of Japanesepatent application 2000-277260 filed on Sep. 12, 2000, the entiredisclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] i) Field of the Invention

[0003] The present invention relates to a phase shift mask blank whichis suitable particularly for ArF or F₂ excimer laser, and amanufacturing apparatus and method of the phase shift mask blank.

[0004] ii) Description of the Related Art

[0005] In recent years, it has been clarified that high resolution andfocus depth are two important properties required for photolithographybut are in a contradictory relation with each other, and that apractical resolution cannot be enhanced only by high NA and shortwavelength of a lens of an exposure apparatus (Monthly SemiconductorWorld 1990.12, Applied Physics Vol. 60, November, 1991, and the like).

[0006] Under such situation, phase shift lithography has been noted asthe next-generation photolithography technique, and partially brought topractical use. The phase shift lithography is a method for enhancing theresolution of photolithography by change only of a mask without changingan optical system. When a phase difference is applied between exposurelights transmitted through the photo mask, mutual interference of thetransmitted lights can be utilized to rapidly enhance the resolution.

[0007] The phase shift mask is a mask for using light strengthinformation together with phase information. Various types of the masksare known such as Levenson type, auxiliary pattern type, andself-matching type (edge emphasizing type). These phase shift masks havea complicated constitution and require a high degree of manufacturingtechnique as compared with the conventional photo mask which has onlythe light strength information.

[0008] In recent years, a so-called halftone type phase shift mask hasbeen developed as one of the phase shift masks.

[0009] In the halftone phase shift mask, a light semi-transmissionportion has two functions: a shield function of substantially shieldingthe exposure light; and a phase shift function of shifting (usuallyreversing) a light phase. Therefore, it is unnecessary to separatelyform a shield film pattern and phase shift film pattern. This type ofphase shift mask is simple in constitution and easy in manufacturing.

[0010] For the halftone phase shift mask, as shown in FIG. 4, a maskpattern formed on a transparent substrate 100 is constituted of a lighttransmission portion (transparent substrate exposed portion) 200 fortransmitting a light which is strong enough to substantially contributeto exposure, and a light semi-transmission portion (shield and phaseshifter portion) 300 for transmitting a light which is not strong enoughto substantially contribute to the exposure (FIG. 4A). Additionally, thephase of the light transmitted to the light semi-transmission portion isshifted, and the light semi-transmission portion is brought to asubstantially reversed relation with respect to the phase of the lighttransmitted through the light transmission portion (FIG. 4B). The lightstransmitted in the vicinity of a boundary between the lightsemi-transmission portion and the light transmission portion and turnedto the opposite portions by diffraction phenomenon cancel each other.Thereby, light strength in the boundary is substantially set to zero,and contrast, that is, resolution of the boundary is enhanced (FIG. 4C).

[0011] The light semi-transmission portion (phase shift layer) in thehalftone phase shift mask or blank needs to have a required optimumvalue with respect to both transmittance and phase shift amount.Concretely, (1) the transmittance in an exposure wavelength of KrF, ArF,or F₂ excimer laser, or the like can be adjusted in a range of 3 to 20%,(2) a phase angle can be adjusted usually to a value in the vicinity of180° in the exposure wavelength, and (3) the transmittance needs to beusually testable in a range of 65% or less in test wavelengths such as257 nm, 266 nm, 364 nm, and 488 nm.

[0012] In recent years, there has been a demand for a finer processingof a device, or the like, and shortening of an exposure wavelength foruse in the device has been advanced. On the other hand, influences of aparticle adhering to the mask blank and a pinhole formed in the maskhave been increasingly regarded as problems. That is, for example, bygeneration of arc in a film formation apparatus during film formation,or other causes, a particle with a particle diameter of about one micronor less is sometimes mixed in the light semi-transmission film at aratio of about 0.05 to 0.5 particle per one square centimeter. Moreover,when there is a fine groove or hole in the surface of a target, theparticle with a particle diameter of about several microns or less issometimes mixed in the light semi-transmission film. When the particlemixed in the light semi-transmission film falls out in a cleaningprocess, the pinhole is generated. Therefore, in order to prepare themask blanks having less pinholes, it is necessary to reduce the numberof particles during formation of the light semi-transmission film.

[0013] Additionally, in conventional mask blanks for i-ray, or KrFexcimer laser, in which a relatively long wavelength is used as theexposure wavelength, there are many particles or pinholes. Therefore,the blanks cannot be applied to some of photo mask blanks for KrF, inwhich a pattern finer than a conventional pattern is formed, or maskblanks for a short wavelength of ArF or F₂ excimer laser.

[0014] With the shortening of the exposure wavelength, a property of theparticle or the pinhole, required for the mask blanks, becomes stricter.It is necessary for practical use of the mask blanks for the shortwavelength of the ArF or F₂ excimer laser to reduce the number ofparticles or pinholes having a diameter larger in size than about a halfof the exposure wavelength as much as possible.

SUMMARY OF THE INVENTION

[0015] The present invention has been developed under the aforementionedbackground, and a first object thereof is to provide a phase shift maskblank in which the number of particles or pinholes each having adiameter larger than a diameter substantially equivalent in size to anexposure wavelength is reduced as much as possible.

[0016] Moreover, a second object of the present invention is to providea manufacturing apparatus and method able to manufacture the phase shiftmask blank in which the number of particles or pinholes each having thediameter larger than the diameter equivalent in size to the exposurewavelength is reduced as much as possible.

[0017] Furthermore, a third object of the present invention is toprovide a photo mask blank in which the number of particles or pinholesis reduced as much as possible.

[0018] Additionally, a fourth object of the present invention is toprovide a manufacturing apparatus and method which can manufacture thephoto mask blank having the number of particles or pinholes reduced asmuch as possible.

[0019] To achieve the aforementioned objects, the present invention hasthe following constitutions.

[0020] (Constitution 1) A manufacturing method of a photo mask blankhaving a thin film for forming a pattern on a transparent substrate,

[0021] wherein during sputtering formation of the thin film, the surfaceof a target is directed downwards and the surface of a substrate isdirected upwards with respect to a gravity direction, and a peripheraledge of the substrate is shielded in order to prevent film formation.

[0022] Particularly, a manufacturing method of a halftone phase shiftmask blank having a light semi-transmission film on a transparentsubstrate,

[0023] wherein during sputtering formation of the lightsemi-transmission film, the surface of a target is directed downwardsand the surface of a substrate is directed upwards with respect to agravity direction, and a peripheral edge of the substrate is shielded inorder to prevent film formation.

[0024] (Constitution 2) A manufacturing method of a photo mask blankhaving a thin film for forming a pattern on a transparent substrate,comprising a step of:

[0025] manufacturing the thin film using a DC magnetron sputteringapparatus comprising at least a sputtering target, a magnetron cathodewith the target attached thereto, a substrate holder disposed oppositeto the target, and a shield disposed on an inner wall of a vacuum tankinside the vacuum tank,

[0026] wherein the surface of a target is directed downwards withrespect to a gravity direction, and

[0027] the apparatus has a mechanism for reducing film formation on anon-sputtered area on the target and the surface of the shield.

[0028] (Constitution 3) The manufacturing method according toconstitution 2 wherein the mechanism for reducing the film formationonto the non-sputtered area on the target comprises a mechanism in whicha whole-surface erosion cathode is used as the magnetron cathode, amechanism for shielding the non-sputtered area on the target, or amechanism for roughening the surface of a non-sputtered portion on thetarget.

[0029] (Constitution 4) The manufacturing method according toconstitution 3 wherein the mechanism for reducing the film formationonto the non-sputtered area on the target further comprises a mechanismfor forming a corner in the target into a curved surface, and rougheningan end surface of the target.

[0030] (Constitution 5) The manufacturing method according toconstitution 2 wherein in the mechanism for reducing the film formationon the shield surface, the shield is kept at a constant temperature, anda shape of the shield is designed so that a relative film formationspeed t in the following equation (i) in at least a shield position inthe vicinity of the target is prevented from being larger than a valuein a position on the substrate:

t=cos θ₁×Sin(θ₁−θ₂)/r ²   (i)

[0031] (in the equation (i), r denotes a distance between a targetcenter and a shield position, θ₁ denotes an angle of a line connectingthe target center to the shield position with respect to a normal of atarget plane, θ₂ denotes an angle of a shield plane with respect to thenormal of the target plane, and t denotes the relative film formationspeed in the shield position defined by r and θ₁).

[0032] (Constitution 6) The manufacturing method according toconstitution 5 wherein in the mechanism for reducing the film formationonto the shield surface comprises a mechanism for forming a corner inthe shield into a curved surface, roughening the surface of the shield,and disposing an earth shield above the target plane.

[0033] (Constitution 7) The manufacturing method according to any one ofconstitutions 2 to 6 wherein the apparatus further comprises a backingplate to which the target is to be attached, and the surface of thebacking plate is roughened.

[0034] (Constitution 8) The manufacturing method according to any one ofconstitutions 2 to 7 wherein the apparatus further comprises a shieldplate for preventing the film from being formed on a peripheral portionof the substrate.

[0035] (Constitution 9) A photo mask blank manufactured using themanufacturing method according to any one of constitutions 1 to 8.

[0036] (Constitution 10) A photo mask blank having a thin film forforming a pattern on a transparent substrate,

[0037] wherein a total number of particles and pinholes having adiameter larger than a diameter substantially equivalent in size to anexposure wavelength for use in the blank as a mask is 0.1 or less persquare centimeter.

[0038] (Constitution 11) A photo mask blank having a thin film forforming a pattern on a transparent substrate,

[0039] wherein an exposure wavelength for use in the blank as a mask hasa center wavelength of 193 nm or less, and a total number of particlesand pinholes having a diameter larger than 0.2 μm is 0.1 or less persquare centimeter.

[0040] (Constitution 12) The photo mask blank according to constitution10 or 11 wherein the thin film for forming the pattern is a lightsemi-transmission-film, and the photo mask blank is a halftone phaseshift mask blank.

[0041] (Constitution 13) A manufacturing apparatus of a photo mask blankfor carrying out the manufacturing method according to any one ofconstitutions 1 to 8.

[0042] (Constitution 14) A photo mask manufactured by patterning a thinfilm in the photo mask blank according to any one of constitutions 9 to12.

[0043] (Constitution 15) A pattern transfer method using the photo maskaccording to constitution 14 to transfer a pattern.

[0044] In the constitution 1, when the target plane is directeddownwards with respect to the gravity direction, the substrate surfacenecessarily turns upwards, and the film is formed on the whole surfaceand side surface of the substrate, but the peripheral edge of thesubstrate is shielded to prevent the film formation as in theconstitution 1. Thereby, particles generated when the film is strippedby handling or cleaning after forming the light semi-transmission filmcan remarkably be reduced, and yield of the mask is remarkably enhanced.This is necessary particularly for the phase shift mask for the shortwavelength of ArF or F₂ excimer laser.

[0045] According to the constitutions 2 to 6, the generation of theparticles from the target plane, shield plane (including the earthshield), or a gap between the target and the earth shield can securelybe prevented. Additionally, respective countermeasures according to theconstitutions 2 to 6 are effective alone. However, a combination of allthe countermeasures can securely prevent the generation of the particlesfrom the target plane, the shield plane (including the earth shield) orthe gap between the target and the earth shield.

[0046] According to the constitution 7, the generation of the particlesfrom a backing plate portion can securely be prevented.

[0047] According to the constitution 8, when the peripheral edge of thesubstrate is shielded by the shield plate in order to prevent the filmfrom being formed on the peripheral edge of the substrate, the particlesgenerated by the film stripped by handling or cleaning after forming thelight semi-transmission film can remarkably be reduced, and the yield ofthe mask is remarkably enhanced. This is necessary particularly for thephase shift mask for the short wavelength of ArF or F₂ excimer laser.

[0048] According to the constitution 9, the photo mask blank having fewdefects can be obtained.

[0049] According to the constitution 10, the total number of particlesand pinholes having the diameter larger than the diameter substantiallyequivalent in size to the exposure wavelength for use in the blank asthe mask is 0.1 or less per square centimeter. Therefore, practical useof the photo mask for the short wavelength of ArF or F₂ excimer lasercan be realized. When the number exceeds 0.1, it is difficult to realizethe practical use of the photo mask for the short wavelength of the ArFor F₂ excimer laser.

[0050] Additionally, even in the present situation, the mask canpractically be used for KrF excimer laser, but the number of particlesand pinholes is further preferably reduced. Therefore, the invention ofthe constitution 10 can be applied to the photo mask blank for KrFexcimer laser, or particularly to some of the photo mask blanks for KrFin which a pattern finer than the conventional pattern is formed.Moreover, the invention can also be applied to a general photo maskblank, because it is preferable to further reduce the number ofparticles or pinholes.

[0051] Here, the substantially equivalent wavelength includeswavelength±20%.

[0052] Additionally, the total number of particles and pinholes having adiameter larger in size than about a half of the exposure wavelength ispreferably 0.1 or less per square centimeter. This range includes ½wavelength±20%.

[0053] According to the constitution 11, the exposure wavelength for usein the blank as the mask has a center wavelength of 193 nm or less, andthe total number of particles and pinholes having a diameter larger than0.2 μm is 0.1 or less per square centimeter. Therefore, the practicaluse of the photo mask for the short wavelength of the ArF or F₂ excimerlaser can be realized. Additionally, the total number of particles andpinholes having a diameter larger than 0.15 μm, preferably larger than0.1 μm is preferably 0.1 or less per square centimeter. This is realizeddepending upon a limitation of sensitivity of a defect test apparatus.In order to detect the particles and pinholes having smaller diameters,the defect test apparatus with a higher sensitivity is necessary.

[0054] According to the constitution 12, the practical use of thehalftone phase shift mask for some of KrF excimer lasers in which thepattern finer than the conventional pattern is formed and for the shortwavelength of the ArF or F₂ excimer laser can be realized.

[0055] According to the constitution 13, it is possible to manufacturethe photo mask blank having few defects.

[0056] According to the constitution 14, the photo mask having fewdefects can be obtained, and the practical use of the photo mask forsome of KrF excimer lasers in which the pattern finer than theconventional pattern is formed and for the short wavelength of the ArFor F₂ excimer laser can be realized.

[0057] According to the constitution 15, the photo mask having fewdefects, and the short exposure wavelength of the KrF excimer laser orArF or F₂ excimer laser can be used to realize a fine patternprocessing.

[0058] The present invention will be described hereinafter in detail.

[0059] In order to achieve the aforementioned objects, as a result ofpursuing of researches, the following has been found.

[0060] Mixture of the particles into the light semi-transmission filmduring sputtering causes stripping of the film attached in a vacuumtank. The particles caused by the stripped film are generated from anon-sputtered portion of the target surface, a gap between the targetand an electrically grounded vacuum tank inner wall (earth shield), afilm attachment preventing component (shield) detachably attached to theinner wall of the vacuum tank, and the like.

[0061] In order to prevent the particles from being generated from thenon-sputtered portion of the target surface, the followingcountermeasures are effective: (countermeasure 1) a whole-surfaceerosion cathode or the like is used to reduce an area of thenon-sputtered portion on the target; (countermeasure 2) thenon-sputtered portion (non-erosion portion) of the target surface isshielded by a shield member; and (countermeasure 3) the non-sputteredportion (non-erosion portion) of the target surface is roughened byblast treatment (treatment for mechanically/physically roughening thesurface).

[0062] The present invention will be described hereinafter withreference to FIGS. 1 and 2, but these are drawings for simpledescription of positions to be subjected to the countermeasures, and theapparatus of the present invention is not limited to forms (e.g., shapesand positional relation (distance) of the respective portions) of thesedrawings.

[0063] The generation of the particle from a gap 13 between a target 5and an earth shield 12 raises a problem, when the whole-surface erosioncathode is used and the end of the target is not shielded with a shieldmember or the like. In order to prevent the particle from beinggenerated from this gap, the following countermeasures are effective:(countermeasure 4) a portion of a corner 5 a in the end of the target isformed into a curved surface (R processed); (countermeasure 5) the blasttreatment or another method is used to roughen a target end 5 b;(countermeasure 6) the blast treatment or another method is used toroughen exposed backing plate surfaces 4 a, 4 b; (countermeasure 7) acorner 12 a of the earth shield is R-processed; (countermeasure 8) thesurface of the earth shield 12 is roughened by the blast treatment oranother method; and (countermeasure 9) the earth shield 12 is disposedabove a target plane d (on a side of the backing plate 4).

[0064] In order to prevent the particle from being generated from theshield portion, (countermeasure 10) improvement of a shield shape iseffective as described later.

[0065] A formation speed t of the film attached to the shield disposedin the vacuum tank can qualitatively be represented by the equation (i)developed by the present inventor.

t=cos θ₁×Sin(θ₁−θ₂)/r ²   (i)

[0066] Here, respective variables in the equation (i) will be describedwith reference to FIG. 1. Variable r denotes a distance between a targetcenter a and a shield position c, θ₁ denotes an angle of a lineconnecting the target center a to the shield position c with respect toa normal e of the target plane, θ₂ denotes an angle of a shield plane 11with respect to the normal e of the target plane, and t denotes therelative film formation speed in the shield position c defined by r andθ₁. Additionally, the shield 11 has a leaf shape in FIG. 1, but theshield 11 may have the leaf shape or a block shape. Moreover, the shield11 is electrically insulated from the earth shield 12, the earth shield12 may be earthed, and a voltage may be applied to the shield 11.

[0067] In the shield position c in the vicinity of the target 5 (area inwhich a value of r is smaller than a distance to the transparentsubstrate with the light semi-transmission film to be formed thereon),it is effective for prevention of the particle generation to design theshape of the shield 11 so that the relative film formation speed t inthe equation (i) is prevented from being larger than the value in theposition on the substrate. In order to satisfy the aforementionedconditions, it is necessary to set a sufficient distance (set r to belarge) between the shield position c to which many films are attached(θ₁ is small) and the target 5 (i.e., the shield 11 in the vicinity ofthe target is disposed apart from the target). It is also necessary toreduce an angle θ₃ of the shield plane in the shield position in thevicinity of the target 5 (with small r) with respect to the target planed (set θ₂ to be large and close to θ₁) (i.e., set the shield plane inthe vicinity of the target to be horizontal with the target plane d).

[0068] In order to prevent the particle from being generated from theshield portion, (countermeasure 11) to remove (R process) a sharp corneror a sharp screw from a portion to which the film is attached on theshield, and (countermeasure 12) to roughen the surface of the shield bythe blast treatment or the like are effective.

[0069] Additionally, (countermeasure 13) to hold the shield to which thefilm is attached by heating at a constant temperature is also effectiveas means for reducing the particle generated from the shield.

[0070] Here, the shield (including the earth shield) in the vicinity ofthe target is heated by a plasma generated on the target or a sputteredparticle from the target. When film formation start and end arerepeated, temperature on the shield changes, and stress of the filmattached to the shield changes with a temperature change. When the filmstress on the shield changes, the film is cracked or stripped, andtherefore the particle is mixed into the light semi-transmission film.When the shield is held at constant temperature, the stress of the filmis also kept to be constant, and the particles generated from the shielddecrease. Optimum temperature of the shield changes with the material ofthe shield or the type of the film. However, in the present invention,when temperature of the shield is controlled to 160° C. from 100° C.,the number of particles mixed in the light semi-transmission film can bereduced.

[0071] When the target surface is directed upwards, the particle adheresto the target surface, this causes abnormal electric discharge, a microgroove and hole are formed in the target surface by the abnormalelectric discharge and the abnormal electric discharge is repeated. Thefilm attached to the particle adhering to target surface or the finegroove or hole is heated by the plasma in the vicinity of the target,evaporation and burst are caused, and the particle or impurity is mixedin the light semi-transmission film. On the other hand, when the targetsurface is directed downwards, the particle does not easily adhere tothe target surface, and therefore the abnormal electric discharge doesnot easily occur. Therefore, in order to form the lightsemi-transmission film having few particles, a sputter down system inwhich the target surface is directed downwards is preferable.

[0072] Additionally, the particle is sometimes generated by filmstripping caused by handling or cleaning after formation of the lightsemi-transmission film. To prevent this, as shown in FIG. 2, there is(countermeasure 15) a method of disposing the shield plate for shieldinga portion 6 a for holding a transparent substrate 6 before and after thefilm formation, and forming no light semi-transmission film on thisportion.

[0073] Additionally, during attaching of the substrate to the substrateholder, the shield plate can preferably be retreated to a position inwhich the attaching of the substrate is not inhibited. Moreover, theshield plate is preferably movable so that a clearance between thesurface of the substrate with the film formed thereon and the shieldplate can be adjusted with high precision (e.g., precision of about 0.1mm) after attaching the substrate to the substrate holder.

[0074] The countermeasures for preventing the particle from beinggenerated in the sputtering apparatus for forming the lightsemi-transmission film have mainly been described above. However,(countermeasure 16) to automate handling until introducing of thetransparent substrate into the sputtering apparatus with a mechanismhaving little particle generation, or to set an atmosphere of asubstrate introduction portion to be in a dust-free state is essentialfor preventing the particle generation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0075]FIG. 1 is a schematic diagram of a main part showing acountermeasure portion of the present invention in a DC magnetronsputtering apparatus.

[0076]FIG. 2 is a schematic diagram of a main part showing thecountermeasure portion of the present invention in the DC magnetronsputtering apparatus.

[0077]FIG. 3 is a schematic diagram of the DC magnetron sputteringapparatus for use in an embodiment.

[0078]FIG. 4 is an explanatory view of transfer principle of a halftonephase shift mask.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0079] Examples of the present invention will be described hereinafterin further detail.

[0080] A DC magnetron sputtering apparatus shown in FIG. 3 was used, acombination of particle countermeasures shown in Table 1 is changed asshown in Table 2, and halftone phase shift mask blanks for ArF excimerlaser (193 nm) were prepared.

[0081] Concretely, a mixed target (Mo:Si=8:92 mol %) of molybdenum (Mo)and silicon (Si) was used to form a nitrided thin film (film thicknessof about 670 angstroms) of molybdenum and silicon (MoSiN) on atransparent substrate by reactive sputtering (DC sputtering) in a mixedgas atmosphere (Ar:N₂=10%:90%, pressure: 0.1 Pa) of argon (Ar) andnitrogen (N₂). In this manner, the phase shift mask blank (filmcomposition: Mo:Si:N=7:45:48) for ArF excimer laser (wavelength of 193nm) was obtained.

[0082] Here, the DC magnetron sputtering apparatus shown in FIG. 3 has avacuum tank 1. A magnetron cathode 2 and substrate holder 3 are disposedin the vacuum tank 1. The sputtering target 5 bonded to the backingplate 4 is attached to the magnetron cathode 2. In the example,oxygen-free steel is used in the backing plate 4, and indium is used tobond the sputtering target 5 to the backing plate 4. The backing plate 4is directly or indirectly cooled by a water cooling mechanism. Themagnetron cathode 2, backing plate 4 and sputtering target 5 areelectrically connected to one another. The transparent substrate 6 isattached to the substrate holder 3.

[0083] The vacuum tank 1 is evacuated by a vacuum pump via an exhaustport 7. An atmosphere in the vacuum tank reaches a degree of vacuumwhich does not influence a property of the formed film, a mixed gascontaining nitrogen is then introduced via a gas introduction port 8, aDC power supply 9 is used to apply a negative voltage to the magnetroncathode 2, and sputtering is performed. The DC power supply 9 has an arcdetecting function, and can monitor an electric discharge state duringsputtering. A pressure inside the vacuum tank 1 is measured by apressure gauge 10.

[0084] A transmittance of a light semi-transmission film formed on thetransparent substrate is adjusted by a type and mixture ratio of gasesintroduced via the gas introduction port 8. When the mixed gas containsargon and nitrogen, the transmittance is increased by increasing a ratioof nitrogen. When a desired transmittance cannot be obtained byadjusting the ratio of nitrogen, oxygen is added to the mixed gascontaining nitrogen, and the transmittance can further be increased.

[0085] A phase angle of the light semi-transmission film was adjusted bya sputtering time, and the phase angle in an exposure wavelength wasadjusted to about 180°.

[0086] In the example, as shown in FIG. 2, a range of about 2 mm fromthe end of a film formed surface of the transparent substrate 6 disposedopposite to the sputtering target 5 is covered with a shield plate 14,so that a light semi-transmission film 20 is prevented from being formedon the holding portion 6 a. Additionally, the holding portion 6 a inFIG. 2 is crosshatched to show the portion, but naturally the lightsemi-transmission film is not formed on the holding portion 6 a.

[0087] Evaluation

[0088] A defect test apparatus (manufactured by KLA-Teucor Co.:KT-353UV) was used to check numbers of particles and pinholes withdiameters of 0.2 μm or more after the film formation, and numbers ofparticles and pinholes with diameters of 0.2 μm or more after thecleaning with respect to an area of 174.2 cm² in the phase shift maskblanks (size: 152 mm square) obtained as described above. Results areshown in Table 2. TABLE 1 Countermeasure No. Particle countermeasure 1Use whole-surface erosion cathode 2 Mask non-erosion portion 3 Blasttreatment of non-erosion portion 4 R-process target end 5 Blasttreatment of target end surface 6 Blast treatment of backing plate 7R-process earth shield 8 Blast treatment of earth shield 9 Improve earthshield plane position 10 Improve shield shape 11 R-process shieldsurface, remove screw 12 Blast treatment of shield surface 13 Shieldtemperature control 14 Sputter down system 15 Shield substrate periphery16 Automate substrate introduction, bring introduction portion todust-free state

[0089] TABLE 2 Effect of particle countermeasure After film formationAfter cleaning Particles Pinholes Particles Pinholes Countermeasure (0.2μm (0.2 μm (0.2 μm (0.2 μm No. or more) or more) or more) or more) 8,12, 14 6311 many 3304 many 8, 12, 14, 13 2836 many 1329 many 8, 12, 14,13, 1 1029 many 448 many 8, 12, 14, 13, 2, 3 1144 many 456 many 8, 12,14, 13, 1, 7 582 many 224 many 11 8, 12, 14, 13, 1, 7 152 12 48 29 11,9, 10 8, 12, 14, 13, 1, 7 72 8 21 12 11, 9, 10, 4, 5, 6 8, 12, 14, 13,1, 7 65 2 13 7 11, 9, 10, 4, 5, 6, 15 all excluding 24 0 5 3 2, 3

[0090] Measurement Area: 174.2 cm²

[0091] As seen from Table 2, with use of the apparatus in which thesputter down system (countermeasure 14), countermeasures 8, 12, 14, 13,7, 11, 9, 10 as a mechanism for reducing the film formation onto theshield surface, and countermeasure 1 as a mechanism for reducing thefilm formation to a non-sputtered area on the target are taken, thenumbers of particles and pinholes after cleaning are in two digits, andare rapidly reduced. Additionally, the countermeasures 10 and 13 arevery effective in the mechanism for reducing the film formation onto theshield surface. Moreover, when the countermeasures 4, 5, 6 are added tothe aforementioned countermeasures, the number of defects is furtherreduced. Furthermore, when the countermeasure 15 is further taken, thenumber of defects is further reduced. The countermeasure 15 forshielding the substrate periphery is very effective, because the defectcan be prevented from being generated during handling of the substrate.

[0092] Moreover, with all the countermeasures (1, 4 to 16) excluding thecountermeasures 2, 3, the halftone phase shift mask blank can beobtained in which the total number of particles and pinholes each havinga diameter (0.2 μm or more) larger than the diameter substantiallyequivalent in size to the exposure wavelength (193 nm) is preferably 0.1or less per square centimeter.

[0093] Moreover, it is seen that the individual countermeasures areeffective, because the number of particles or pinholes decreases.

[0094] Additionally, in the conventional mask blanks for i-ray, or KrFexcimer laser, in which the target surface is directed upwards and thefilm is formed in an in-line type sputtering apparatus, there are manyparticles or pinholes. Therefore, it has been confirmed that theseblanks cannot be applied to the mask blanks for the short wavelength ofthe ArF or F₂ excimer laser.

[0095] The preferred examples of the present invention have beendescribed above, but the present invention is not limited to theaforementioned examples.

[0096] For example, the method and apparatus of the present inventionare applied to the halftone phase shift mask blanks having the lightsemi-transmission film in the aforementioned embodiment, but the presentinvention is not limited to the embodiment. For example, the method andapparatus of the present invention may be applied to the photo maskblank which has a shield film formed of chromium or a chromium compound.

[0097] Additionally, molybdenum was used as a metal constituting thelight semi-transmission film, but this is not limited, and zirconium,titanium, vanadium, niobium, tantalum, tungsten, nickel, palladium, andthe like can be used.

[0098] Moreover, the target of molybdenum and silicon was used as thetarget containing metal and silicon, but this is not limited. In thetarget containing metal and silicon, molybdenum is particularly superioramong the aforementioned metals in controllability of the transmittanceand in that a target density increases and particles in the film can bereduced with use of the sputtering target containing metal and silicon.Titanium, vanadium, and niobium are superior in resistance to analkaline solution, but slightly inferior to molybdenum in the targetdensity. Tantalum is superior in the resistance to the alkaline solutionand target density, but slightly inferior to molybdenum in thecontrollability of transmittance. Tungsten has properties similar tothose of molybdenum, but is slightly inferior to molybdenum in anelectric discharge property during sputtering. Nickel and palladium aresuperior in the optical property and resistance to the alkalinesolution, but dry etching is slightly difficult to perform. Zirconium issuperior in the resistance to the alkaline solution, but inferior tomolybdenum in the target density, and the dry etching is slightlydifficult to perform. Considering these, molybdenum is most preferableat present. Molybdenum is also preferable for a nitrided molybdenum andsilicon (MoSiN) thin film (light semi-transmission film) in superiorchemicals resistance such as acid resistance and alkali resistance.

[0099] Furthermore, in order to obtain the thin film of a composition inwhich electric discharge stability is secured during film formation andvarious properties of the phase shift mask are satisfied, the targetcontaining 70 to 95 mol % of silicon, and metal is preferably subjectedto DC magnetron sputtering in the atmosphere containing nitrogen.Thereby, the light semi-transmission film containing nitrogen, metal andsilicon is preferably formed.

[0100] When the content of silicon in the target is larger than 95 mol%, a voltage is not easily applied (electricity is not easily passed) toa target surface (erosion portion) in the DC sputtering, and theelectric discharge becomes unstable. Moreover, when the content ofsilicon is less than 70 mol %, the film constituting a lightsemi-transmission portion with a high transmittance cannot be obtained.Furthermore, electric discharge stability is further enhanced bycombination of the nitrogen gas with the DC sputtering.

[0101] Additionally, the electric discharge stability during filmformation also influences film quality. When the electric dischargestability is superior, the light semi-transmission film with asatisfactory film quality is obtained.

[0102] Furthermore, in the manufacturing apparatus and method of thepresent invention, there can be,provided a constitution in which thetransparent substrate is disposed opposite to the target with a certainangle, the substrate is rotated, and the film is formed by inclinedsputtering.

[0103] As described above, according to the phase shift mask blank ofthe present invention, the total number of particles and pinholes eachhaving a diameter (particularly larger than 0.2 μm) larger than thediameter substantially equivalent in size to the exposure wavelength inthe light semi-transmission film is preferably 0.1 or less per squarecentimeter. Therefore, the practical use of the phase shift mask for theshort wavelength of the ArF or F₂ excimer laser can be realized.

[0104] Moreover, according to the manufacturing apparatus and method ofthe phase shift mask blank of the present invention, it is possible tomanufacture the phase shift mask blank in which the total number ofparticles and pinholes each having a diameter (particularly larger than0.2 μm) larger than the diameter substantially equivalent in size to theexposure wavelength in the light semi-transmission film is preferably0.1 or less per square centimeter.

[0105] Furthermore, according to the present invention, there can beprovided the photo mask blank in which the number of particles orpinholes is reduced as much as possible.

[0106] Additionally, there can be provided the manufacturing apparatusand method able to manufacture the photo mask blank in which the numberof particles or pinholes is reduced as much as possible.

What is claimed is:
 1. A manufacturing method of a photo mask blank having a thin film for forming a pattern on a transparent substrate, comprising steps of: directing the surface of a target downwards and the surface of a substrate upwards with respect to a gravity direction; shielding a peripheral edge of said substrate to prevent the film from being formed on the peripheral edge; and sputtering/forming said thin film.
 2. A manufacturing method of a photo mask blank having a thin film for forming a pattern on a transparent substrate, comprising a step of: manufacturing said thin film using a DC magnetron sputtering apparatus comprising at least a sputtering target, a magnetron cathode with the target attached thereto, a substrate holder disposed opposite to said target, and a shield disposed on an inner wall of a vacuum tank inside the vacuum tank, wherein the surface of a target is directed downwards with respect to a gravity direction, and the apparatus has a mechanism for reducing film formation on a non-sputtered area on the target and the surface of the shield.
 3. The manufacturing method according to claim 2 wherein said mechanism for reducing the film formation onto the non-sputtered area on the target comprises a mechanism in which a whole-surface erosion cathode is used as the magnetron cathode, a mechanism for shielding the non-sputtered area on the target, or a mechanism for roughening the surface of a non-sputtered portion on the target.
 4. The manufacturing method according to claim 3 wherein said mechanism for reducing the film formation onto the non-sputtered area on the target further comprises a mechanism for forming a corner in the target into a curved surface, and roughening an end surface of the target.
 5. The manufacturing method according to claim 2 wherein the mechanism for reducing the film formation on the shield surface keeps the shield at a constant temperature, and a shape of the shield is designed so that a relative film formation speed t in the following equation (i) in at least a shield position in the vicinity of the target is prevented from being larger than a value in a position on the substrate: t=cos θ₁×Sin(θ₁−θ₂)/r ²   (i) (in the equation (i), r denotes a distance between a target center and a shield position, θ₁ denotes an angle of a line connecting the target center to the shield position with respect to a normal of a target plane, θ₂ denotes an angle of a shield plane with respect to the normal of the target plane, and t denotes the relative film formation speed in the shield position defined by r and θ₁).
 6. The manufacturing method according to claim 5 wherein the mechanism for reducing the film formation onto said shield surface comprises a mechanism for forming a corner in the shield into a curved surface, roughening the surface of the shield, and disposing an earth shield above the target plane.
 7. The manufacturing method according to claim 2 wherein the apparatus further comprises a backing plate to which the target is to be attached, and the surface of the backing plate is roughened.
 8. The manufacturing method according to claim 2 wherein the apparatus further comprises a shield plate for preventing the film from being formed on a peripheral portion of the substrate.
 9. A photo mask blank manufactured using the manufacturing method according to claim
 1. 10. A photo mask blank manufactured using the manufacturing method according to claim
 2. 11. A photo mask blank having a thin film for forming a pattern on a transparent substrate, wherein a total number of particles and pinholes having a diameter larger than a diameter equivalent in size to an exposure wavelength for use in said blank as a mask is 0.1 or less per square centimeter.
 12. A photo mask blank having a thin film for forming a pattern on a transparent substrate, wherein an exposure wavelength for use in said blank as a mask has a center wavelength of 193 nm or less, and a total number of particles and pinholes having a diameter larger than 0.2 μm is 0.1 or less per square centimeter.
 13. The photo mask blank according to claim 11 wherein said thin film for forming the pattern is a light semi-transmission film, and said photo mask blank is a halftone phase shift mask blank.
 14. The photo mask blank according to claim 12 wherein said thin film for forming the pattern is a light semi-transmission film, and said photo mask blank is a halftone phase shift mask blank.
 15. A manufacturing apparatus of a photo mask blank for carrying out the manufacturing method according to claim
 1. 16. A manufacturing apparatus of a photo mask blank for carrying out the manufacturing method according to claim
 2. 17. A manufacturing apparatus of a photo mask blank for carrying out the manufacturing method according to claim
 3. 18. A manufacturing apparatus of a photo mask blank for carrying out the manufacturing method according to claim
 4. 19. A manufacturing apparatus of a photo mask blank for carrying out the manufacturing method according to claim
 5. 20. A manufacturing apparatus of a photo mask blank for carrying out the manufacturing method according to claim
 6. 21. A manufacturing apparatus of a photo mask blank for carrying out the manufacturing method according to claim
 7. 22. A manufacturing apparatus of a photo mask blank for carrying out the manufacturing method according to claim
 8. 23. A photo mask manufactured by patterning a thin film in the photo mask blank according to claim
 9. 24. A photo mask manufactured by patterning a thin film in the photo mask blank according to claim
 10. 25. A photo mask manufactured by patterning a thin film in the photo mask blank according to claim
 13. 26. A photo mask manufactured by patterning a thin film in the photo mask blank according to claim
 14. 27. A pattern transfer method using the photo mask according to claim 23 to transfer a pattern. 